Fotor Photo Editor

Fotor is a free web application powered by HTML 5, it offers basic photo adjustment and most surprisingly, a great one-click HDR feature. Check the video below:

No installation needed, you just have to go to its website, or by installing the Web Apps here.

Pixlr

Pixlr took the function offered by Fotor even deeper. It can do layering task as well as blending mode, just like in Photoshop. Like Fotor, Pixlr needs no installation. All you need is the internet connection.

GIMP

Unlike both samples above, GIMP runs natively on your computer. It supports all operating system. Like Pixlr, it can deal with layers, blending mode and transparency. By far, GIMP is the closest to Photoshop in this list.

Polarr

I can’t believe that this is a freeware. With a very nice GUI and user-friendly user interface, it offers even wider adjustment option than the others. If you need a quick editor, then this is your tool. If you want to spend hours polishing your photos, Polarr will also come in handy. Have I mentioned that it’s available offline too?